Mahao was allegedly gunned down by soldiers at his home outside of the capital Maseru. Observers in Lesotho believe it was part of a campaign being led by the current army chief Tlali Kamoli against supporters of the former Prime Minister Tom Thabane.
Mapisa-Nqakula was accompanied by the foreign ministers of Zimbabwe and Namibia, according to South African government officials.
The fact-finding mission was launched by President Jacob Zuma, as current chair of the security organ of the Southern African Development Community (Sadc) as well as the Sadc secretariat.
Mapisa-Nqakula told the SABC on Sunday that the delegation had met Lesotho Prime Minister Pakalitha Mosisili, King Letsie III, leaders of the opposition and church leaders.
She did not specify which opposition leaders they met. Thabane and at least two other opposition leaders are believed to have fled to South Africa, fearing that they will be targeted next.
Mapisa-Nqakula said that Lesotho had had free, fair and peaceful elections in February “and whatever has happened since needs to be properly investigated”.
Lesotho Defence Minister Tseliso Mokhosi told SABC News that Mahao had been killed by soldiers and so his death should not be linked to the politics of the country.
But few people in Lesotho appear to believe that is true.
On Thursday night after Mahao’s death, Mokhosi had announced that “a soldier” – whom he did not name – had been killed by Lesotho Defence Force soldiers after resisting arrest.
But Mahao’s son who was with him when he was shot, told relatives that he had thrown up his arms in surrender when three army truckloads of soldiers stopped his car. They shot him anyway.
Mahao had been an ally of Thabane and a rival to Kamoli. It was the decision of Thabane – then still prime minister – to fire Kamoli and replace him with Mahao that prompted Kamoli to attack both Thabane and Mahao’s homes on August 30 last year. Both narrowly escaped and fled to South Africa.
Deputy President Cyril Ramaphosa was appointed by Sadc to resolve the crisis. He brokered a deal to bring forward elections from 2017 to February this year when a Mosisili-led coalition defeated Thabane.
Mosisili immediately reappointed Kamoli as army chief and local journalists say that’s when a reign of terror began against Thabane loyalists.
Recently, prominent businessman Thabiso Tsosane, a good friend of Thabane and funder of his All Basotho Convention (ABC) was also shot dead shortly after meeting Thabane in Maseru.
And several soldiers accused of plotting to overthrow the Mosisili government were arrested and appeared to have been assaulted and tortured when they eventually appeared in court.